Cover for manholes or the like



Sept. 19; 1944. c. G. WALKER HAL. 2,35 7

COVER FOR MANHOLES OR THE LIKE Filed Aug. 26, 1942 I I V Q-. Z6

Patented Sept. 19, 1944 U N lTE-D STATES PATENT QFFPI CE 1 coma-Foe. MANHOLES: onizrnn. mm Charles G; Walker. "Skokie. 111., andfljHerman 'Frauenfelder, .StJLonis, Mo, assignors to'Cast Stonelnstitute, Washington,"D.-'C.,*anmnin- I --corporatedassociation ApplioationAugustZfi, 1942;1Serial NO-i 456,280

7 "10 Claims. (01172-100) Our inventions-relates to c'overs'for manholes and; the .likesa-nd more especially provides certain improvements-by whichsuchrcovers may-be made withya': minimum of metal. :without sacrificingstrength, durability, economy of manufacture; ease 10f. handling; lightness of weight, and a desirable minimum off-bulk.

.Generally speaking these and other important objects are accomplished :byl fashioning. the-cover mainly from. concrete 01" the like and providing. it --wit-h arr-outer- -metallic rimrand :an inner skeleton metallic. reinforcing assembly of novelwtype which cooperates with the concrete and-thezrim insuch away that therrim and concrete take all loads in compress-ion while the inner: metal. takes all loads in tension.

"In additionto the saving ofimetal as compared with-conventional all-metal covers zor 'the best composite metal and concrete covers ofthe prior artknownto us, our new construction possesses certain important advantages which: give it structural and functional superiority. "Referenceto some :of .theseradvantages. has been made hereinabove, and other will be apparent to -those skilled inthe art from a consideration of-the-following specification taken in' conju-nction with the annexed drawing which illustratesthe invention in .7 certain embodiments which have been reduced. to. actual practice, thoroughlytested and found to be entirely" satisfactory, so that they areatpresent preferred by us.

Inthe drawing,

"Figure .1 is- :a .top plan .viewof eacover constructed in accordancewiththe principles of. the

present invention, with its reinforcing assembly The cover .is .shown shown in broken lines. mounted in place in a manhole frame.

'Fig. '2 is a side elevational view of the'frame andcover; these two parts beingshown vertically separated.

Fig. '3 is a diametric vertical sectionthroughj the associated fram and cover takenflon theline 33- of-Fig. 1 showingthe parts in a portionfof pavement. 1

Fig.4 is a top plan view of the reinforcing frame or assembly used intlie cover. Y

Fig.5 is-a perspective view of-part'of thereinforcing frame or assembly with one edge "of the view cut along thesection line 55 of Fig. '4.

"FiggG is a detailsectional-viewtaken on the line 66 of Fig. 1.

7 isa top-plan view of -a modifiedfior-mof cover. Fig. '8i-is-a diametric sectionta-ken on thei'line 88of "Fig. 7. a,

Referring to -the drawing, "and :first :to Fig. I 3 thereference numeral I'D designates any conventionalvault. orchamber in astreet, sidewalk or" thelike, surmounted-by a manhole frame H,

here shown as of generallyhollow cylindrical shapegbut provided-in: its lower portion with an outwardly'radial base flange l2;overlaid:by a1 pave ing surface-l3i .The top inner. margin ofthis frame is formed .with avseat indentation l4ffor.

a manhole cover,=-as is conventional in these cone structions. The frame maybe made mainly of ccncretenor the: like and details of its construction-inay include "a protective edging of metal 01" its *top, vmetal reinforcing means, embedded eyes for engagement :by lifting hooksyvertical' holes in its bottom flange, etc. In the illustrated frame the-top edge is: protected by a hoop or ring P5 of angle iron with its two flanges set respectivelyvrin the: vertical wall of'the cover seat [4 and :inthe extreme top surface of the frame which is approximatelyfiush with the pavement surface l3. 'Ifdesired, thisv ed-gingmay comprise merelya fiat. annulusifor, protecting only; the top surface of the frame-rit maybe of U-shape in cross section to protectznot-only. the extreme top surface of the frame-but also-the vertical surface of: the cover sea-tor it maybe of Z-shape-in cross ?section"to protect also the horizontal surf, V

facezof the seat- 'In x the illustrated construction, vertical reinforcing stirrups l6 depend. at circumferentially spaced intervals from'thering and annular bar; reinforcing members I! are embeddedin the lowernportion of the frame. Stout wire eyes'. I8 project from cavities I 9 in the outer side :of the frame, and holes 20. areicored through the base flange.- All these detai1s=may .be varied-widely;

' this-illustration that the slab .21 is a'Portland The cover, tocvhich thisinventionparticularly relates..-comprises essentially a unitary .or mono lithicwslabxll of concreteor other-cementitiousf orrplastic-material which can bei cast and caused t ..harden. .Hereinafterspecific.suggestions fore. practical material will begiven, but: it isto be understood that ta very considerable choice is available-andthat the invention is not to be con sidered limited to the use of any specific 1 substance. Let-it; be assumed for the purposes of cement concrete mix of thegeneral,typeusedifor' paving.

Embedded in the slab 21 isr-the reinforcing" framework or assembly generally designated zl and best shown in Figs. 4 and: 5. The illustrated cover iSIOf circular shape, andconsequentlythe reinforcing frame isigenera-lly"wheelalike'in pattern. .As will be observed; .its"principa;1.

ments include'an outer ringor rim .23, an inner ring 24', andiradiating; ci'rcumferentiallyspaced rod 25-'-which are fixeds'at their inner ends'to the. ring 2,4 and: at their L'outer ends to: the ring or:rim-2 3. An.intermediatefringizfi may-if de-. sired be' included; .1 inrwhiche case the rods are" securedzto :suchr'ring tasrby welding. i

:Thginlle! wing or thezinnerl'and; intermediate rings arez'concentric withtthe onter. ring,1here-"- inafter called simply the rim, and the inner ring is spaced below the plane of the rim. The rods.

may be made fast to the rim and to the inner ring in any practical way, as by the welds indicated in the drawing. A convenient connection between the rods and the inner ring consists in hooking the ends of the rods around'the ring It could be made of strap iron, in which case concrete has inherently high compressive strength, it will be appreciated that the composite structure is exceedingly strong and resistant to load strains.

. The structure shown in Figs. 7 and 8 diifers from the previously described embodiment in that certain limited areas of the slab are cored out between rods to provide openings 3| and the center is similarlyprovided with an opening 32, so that this cover may serve as a grating or drain, or it may be used as a ventilating the rim would not have either of the inwardly :3

directed flanges 21 but would have only its web.-

28, or it could be made of angle stock, in which case it would have its web and one flange; We prefer to use channel stock and toaflix the rods to the web of the channel, as shown. I

' To make thecover, the reinforcing framework 22' is placed in" a mold (not shown) whose cavity is shaped with surfaces to engage snugly and seat the web 28 and the bottom flange 21 of the rim. The remainder of the mold cavity is formed toproduce the casting shape'shown possessed by'thecover slab in Fig. 2. That is'to say, the cavity has a depressed circular center with walls sloping up therefrom to about the level of the surface on which the lower flange 21 rests so that the center of the mold cavity is a pocket of inverted frusto-conical o-r frusto-pyramidal shape to give the casting" the central boss 28. Between this pocket and the outer wall of the 'cavityfth'e 'mol'd bottom is channeled radially upwardly and outwardly to form on the casting the stout ribs shown at '29. The mold cavity is sosproportioned with respect w the. reinforcing framework 22 that when the framework 'is s'et in the cavity, withthe lower flange 21 resting on the cavity seat formed to receive it, the inner ring 24' of the framework will be spaced somewhat above the mold bottom which forms the central pocket and each of the rods 25 will be aligned along the center of one of the'mold channels which will form the ribs 29. A -suitable mix is then poured into the mold and leveled oil fiush' with the 'top flange-210i the manhole cover or a catch basin cover.

It'will be appreciated that the skeletonized arrangement of the reinforcing framework is well adapted to permit such openings as these to be formed inthe casting; while the fact that the concrete reacts in compression to loads encountered in service means that the strength of such a cored out construction is not appreciably impaired. In cases where the intermediate ring 26 is omitted, the openings 3! may be made considerably larger than as shown in Figs. '7 "and 8.

While of course specific dimensions and proportions are no part of the inventive concept, we'think it will'be helpful to this disclosure to state some of the principal dimensions to which we have made and tested certain commercial embodiments.

In a cover for a 24 inch opening, the external diameter of the rim 23 is 23 /;inches. The channel stock from which this rim is formed is 1 inch overall between outer surfaces of the flanges framework. Preferably the mold is vibrated or I otherwise treated to minimize voids and make the casting as dense as-possible. Upon hardening o'f-the casting the mold is stripped and if necessary the casting is cured in any suitableway.i 'Theresult: is a unitary slab as shown in Fig. 2, having a generally'flat topfor one that is slightly crowned if desired, edged by the rim 23,'and having a bottom configured by ribs 29 and a central boss 28 encasing respectively the rods 25 and the inner ring. of the reinforcing framework. This isthe complete cover-of Figs.

1,, 2 andj 3, except for such incidental details as the lift openings 30 which may be formed by inserting short pipe lengths in the mix toserve as'line'rs.

In place in a pavement as shown in Fig. 3, the

axial tension, by the rim 23 resisting'contrab tion, and by the body of concerte positioned inwardly of the rim actingincompression to resist th tendenc'yiof the rim to compress it. Since the metal, which" ispreferably iron or steel, has inherently high tensile strength, while the 21,'so. that the outer edge thickness of the cover isl inch. The 'center'thlckness is 4 inches and the boss 28 is 6 inches in diameter at its bot-- tom face. The rods 25 are twelve in number as shown and are made of ir'rch bar stock. The inner ring 24 isof inch stock, 6 inches in diameter. These dimensions will indicate the approximate proportions in which a thoroughly practical commercial embodiment of the invention' may'be made. v

We have used with success as the material for theslab a mix'known as 7500 pounds per square inch concrete, which consists of 4 parts accurately graded aggregate, 1 part Portland cementj and 4 part water, all by weight. This casting was cured by keeping it damp for 21 days.

In the illustrated embodiments the covers are shown as of circular shape, but it will be obvious that other shapes may be designed. without departingfroln theprinciples of the invention.

Hence the terms ,ring and the like used-in. this specification and in the appended claims are notto be taken as necessarily implying circular,shape.,,;

if Sin'c it is possible to incorporate in the new are commonly made with edges approximately 1 inch thick. Frameseats already in place made to receive such covers will 1y well receive the new covers.

'Ihe essential principlesof the invention are defined by the appended claims. The specific features of construction explained hereinabove and shown in the drawing maybe modified withiri i those principles, and all such"modiflcations" to the extent that they are within the? spirit of 'the'invention as pointed outby 'th'e claims are to be deemed within the scope and;

purview of the claims.

of course equal- 1. A cover for a manhole or the like comprising a reinforcing structure including a continuous outer metallic rim, an inner metallic ring concentric with the rim and below the level there= of, and a plurality of circumferentially spaced radial metallic rods inclined upwardly from the ring to the rim rigidly connected at their op|posite ends to the rim and ring respectively, and a filling of concrete covering the ring and rods and adapted to be placed in compression by loads on the cover. I

2. A cover for a manhole or the like comprising a reinforcing structure including a continuous outer metallic rim, an inner metallic ring concentric with the rim and below the plane thereof, and a plurality of circumferentially spaced radial metallic rods rigidly connected at their opposite ends to the rim and ring respectively, and a filling of concrete covering the ring and rods and peripherally bounded by the rim, said filling having a substantially plane upper surface and being appreciably thicker at its central portion than at its periphery, whereby the rods are tensioned and the filling is compressed by loads on the cover.

3. A cover for a manhole or ing a reinforcing structure ous outer metallic rim, an inner metallic ring concentric with the rim and below the plane thereof, and a plurality of circumferentially spaced radial metallic rods rigidly connected at their opposite ends to the rim and ring respecthe like comprisincluding a continutively, and a filling of concrete covering the ring and rods and peripherally'bounded by the rim, said filling having a substantially plane upper surface and being appreciably thicker at its central \portion than at its periphery and including ribs outstanding from its under surface, each rib enclosing one of the rods of the reinfoncing structure, whereby the rods are tensioned and the filling is compressed by loads on the cover.

4. A cover for a manhole or the like comprising a reinforcing structureinoluding a continuous outer circular metallic rim of channel shape, an inner metallic ring concentric with the rim and below the plane thereof, and a plurality of circumferentially spaced radial metallic rods having their inner ends secured to the ring to resist outward pull and having their outer ends welded to the web of the rim, and a filling of concrete covering the ring and rods and extending into the rim, said filling having a substantially plane upper surface and being appreciably thicker at its central portion than at its periphery and in-- cluding ribs outstanding from its under surface, each rib enclosing one of the rods of the reinforcing structure, whereby the rods are tensioned and the filling is compressed by loads on the 'cover.

5. A cover for a manhole Or the lik comprising a unitary concrete slab having a thickened central portion, a relatively thin peripheral edge, a substantially fiat upper surface and a plurality of ribs on its under surface radiating from the central portion upwardly and outwardly to said peripheral edge, in combination with a metallic reinforcing framework comprising a continuous rim bounding and seating said edge of the slab, a ring embedded in the central portion of the slab below the plane of the rim, and circumferentially spaced radiating rods fixed to the ring and to the rim and each embedded in a rib,

whereby a load on the upper surface of the slab 6. A cover for a manhole Or the like compris- I ing a unitary concrete slab having a thickened central portion, a relatively thin peripheral edge, a substantially flat upper surface, and portions of its under surface upwardl and outwardly inclined from the central portion to said peripheral edge, in comb'nation with a metallic reinforcing framework comprising a continuous rim bounding and seating said edge of the slab, a rin embedded in the central portion of the slab below the plane of the rim, and-circumferentially spaced radiating rods fixed to the ring and extending upwardly and outwardly to fixed engagement with the rim, whereby a load on the upper surface of the slab places the concrete in compression both axially and radially and places the rods in tension and the rim in compression.

'7. A skeleton metallic reinforcing framework adapted to be embedded in a concrete coverfor a manhole or the like comprising a continuous outer rim, an inner ring concentric with the rim and below the plane thereof, and a plurality of circumferentially spaced rods rigidly connected at their inner ends to the ring and radiating outwardly and upwardly to th rim with their extreme outer ends welded to the rim so as to resist separation from saidv rim and ring when subjected to tension.

8. A skeleton metallic reinforcing framework adapted to be embedded in a concrete cover for a manhole or the like comprising a continuous outer rim in the form of an endless inwardly facing channel, an inner ring concentric with the rim and below the plane thereof, and a plurality of circumferentially spaced rods rigidly connected attheir inner ends to the ring and radiating outwardly and upwardly to the rim with their outer ends welded to the inner face of the web of the rim.

9. A cover for a manhole or the like comprising a concrete slab having a thickened central portion and a reltaively thin peripheral portion ward the geometrical center point of the cover and inclined downwardly from the plane of the rim, and means forming part of said framework securing said rods rigidly together in a zone of 1 said thickened central portion around said cen-' ter point.

10. A cover for a manhole or the like comprising a concrete slab having a thickened central portion and. a relatively thin peripheral portion and a metallic reinforcing assembly embedded in the slab between its peripheral edge and a zone surrounding and spaced from the geometrical center of the cover, said assembly comprising a continuous rim defining the outside of the assembly and a plurality of rod portions rigidly connected together in said zone below the plane of the rim and inclined upwardly and outwardly with their outer ends rigidly secured to the rim, whereby loads on the central portion of the slab are resisted by tension in the rod portions and compression in the slab. 7

CHARLES G. WALKER. HERMAN FRAUENFELDER. 

